This invention relates to jet-textured multifilament yarn of side-by-side bicomponent filaments, and is more particularly concerned with providing textured polyester yarn which has yarn bulk and filament crimp aesthetics characteristic of monocomponent set-textured polyester yarn produced by false-twist texturing, and has advantages thereover of freedom from torque, less glitter and enhanced dyeability.
Continuous-filament polyester yarns of monocomponent filaments which have been false-twist textured and then heat set to remove a substantial amount of torque constitute the great majority of yarns used for knitted or woven apparel fabric where bulk, cover and warmth are desired along with the wrinkle resistance and other desirable properties characteristic of polyester yarns. False-twist texturing is accomplished by introducing twist in yarn as it passes over a heater, cooling the twisted yarn and then untwisting the yarn. Seem et al. U.S. Pat. No. 3,785,135 is concerned with the problem created by torque set in the yarn by false-twist texturing, and discloses methods of reducing the amount of torque without removing too much of the crimp set in the filaments. The untwisted yarn can be reheated under carefully controlled conditions of temperature and tension, either in package form or during passage over a second heater. Residual torque can be further reduced by reverse twisting the yarn during the second heating. The combination of treatments requires considerable time and uniform textured yarn is difficult to produce.
Bosley U.S. Pat. No. 3,454,460 discloses production of side-by-side bicomponent polyester fibers for use in staple-spun yarn. Examples I and III illustrate melt-spinning either poly(ethylene terephthalate/isophthalate) or poly(ethylene/2,2-dimethyl-1,3-propylene terephthalate) as one component and poly(ethylene terephthalate) as the other component of the bicomponent fiber. Crimp is developed in the fibers by heating to a temperature of approximately 100.degree. C. or reasonably above, preferably after being woven into fabric. Example II illustrates staple-spinning the fibers into yarn, weaving the yarn into fabric, and developing the crimp when the fabric is scoured and bleached at the boil. The crimp obtained is adequate for conventional uses of staple-spun yarn, but is quite inadequate for the uses of false-twist textured, heat set, polyester yarn of continuous filaments.